1. Field of the Invention
This invention relates to the remineralization of process water in a desalination process. More particularly, the present invention relates to using carbon dioxide sequestered from seawater, or concentrates called brines, to remineralize desalinated water produced using membrane processes, thermal processes, or other alternative processes.
2. Description of the Background Art
Known desalination systems use reverse osmosis (RO) filters, or thermal energy, or electrical current, to create pure water (H2O) from seawater. Desalinated water by itself, however, is not suitable for human consumption and is highly corrosive to distribution systems, such as pipelines and plumbing. This is because pure processed water has a lower pH by dissolution of carbon dioxide in atmosphere and is devoid of key minerals. Thus, known desalination systems require a post-treatment or remineralization process. In this process minerals, such as calcium and carbonates, are added back to the desalinated water. This remineralization step adds taste and reduces the corrosive effects of the water.
Known remineralization processes add gaseous carbon dioxide (CO2) and either calcium hydroxide (Ca(OH)2) or calcium carbonate (CaCO3). These react with the water (H2O) to form a soluble calcium bicarbonate(Ca(HCO3)2). Calcium bicarbonate (Ca(HCO3)2) increases the pH and otherwise adds both alkalinity and hardness to the water. The result is water that is better tasting and less corrosive. Current remineralization techniques deliver the gaseous carbon dioxide (CO2) via commercial suppliers or the on-site burning of fossil fuels. However, commercial carbon dioxide (CO2) supplies can be expensive and can substantially increase the price per gallon of the resulting water. On-site burning of fossil fuels is also not an acceptable alternative due to the creation of damaging green house gases.
Thus, there exists a need in the art for a remineralization processes that does not require an external supply of carbon dioxide (CO2). There is also a need in the art for a remineralization process that is more cost effective and that is not damaging to the environment.
The present invention is aimed at fulfilling these needs.